Solar panels can convert clean and inexhaustibly-supplied solar energy directly to electric energy and therefore are expected as novel energy sources. Silicon substrates are used for current mainstream solar panels. A collector electrode containing silver is provided on the surface of a silicon substrate. With the use of silver as a material for the collector electrode, it has been attempted to reduce the contact resistance between the silicon substrate and the collector electrode and to suppress the resistance of the collector electrode itself (for example, see Japanese Unexamined Patent Application Publication No. 2009-194013).
Further, a wide width of the collector electrode provided on a light receiving side of a solar panel reduces the opening area of the silicon substrate to achieve inefficient energy conversion. Accordingly, it has been proposed to form an electrode in which a conductive layer containing silver is layered to reduce the reduction in the opening area and reduce the resistances (for example, see Japanese Unexamined Patent Application Publication No. 2010-090211). JP No. 2010-090211 discloses that a conductive layer containing silver is layered by printing to reduce the specific resistance and suppress oxidation.